What is the excitation current of a transformer?

Transformer excitation current.

It's a synchronous motor.

The current flowing through the rotor (with this current, the rotor acts like an electromagnet.

There are n poles and S poles), and during normal operation, this current is generated by a DC voltage applied externally to the rotor.

This DC voltage is determined by the DC motor.

supply, developed to mostly by thyristors.

After rectification, the thyristor rectifier system is usually called an excitation device.

Expansion: The excitation transformer is a device that provides three-phase AC excitation power supply for the generator excitation system, and the excitation system converts the three-phase power supply into the DC power supply of the generator rotor through the thyristor, forming the generator excitation magnetic field, and adjusting the SCR trigger angle through the excitation system to achieve the purpose of adjusting the motor terminal voltage and reactive power.

When the generator is running alone, the excitation regulator adjusts the terminal voltage of the generator by adjusting the excitation current of the generator, when the power system.

When multiple generators are running in parallel, the excitation regulator adjusts the excitation current to reasonably distribute the reactive power between the generator sets running in parallel.

This improves the static and dynamic stability of the power system.

Excitation is a machine that provides stator power to the stator of a generator or synchronous motor, and provides a working magnetic field for the generator or other electrical equipment (electrical equipment that works using the principle of electromagnetic induction). Sometimes a device that provides rotor power to the rotor of a generator is also called excitation.

According to the different excitation methods of the DC motor, it can be divided into other excitation, and excitation, string excitation, compound excitation, etc., in the rotation process of the DC motor, the excitation is to control the voltage of the stator to make the magnetic field change, change the speed of the DC motor, and change the excitation also plays a role in changing the speed.

The cross-linking and mutual inductance of magnetic flux is the principle of power transmission between the primary and secondary sides of the transformer. When the primary coil of the no-load transformer is connected to the power supply voltage, the inflow current is the excitation current, also called the excitation current, and the magnitude of this current is proportional to the leakage and DC resistance of the coil. If these two factors are ignored, then u0 = e0 = and excitation current = 0.

where u0 is the supply voltage and e0 is the coil self-inductance potential. However, because in fact, although the coil resistance is very small, the magnetic flux leakage is also very small, after all, it is not 0, therefore, u0 is slightly greater than e0, and this difference causes the excitation current to not be 0

For civil small models and small power transformers, a 40-watt 6-lamp tube radio transformer has a current of only 20 milliamperes when it is not loaded. For a full load of about 200 milliamps, it is only about one-tenth of it.

When the transformer secondary is loaded, the excitation current still exists, or as large as the original, and the total current of the primary is equal to the excitation current + the current converted to the primary level.

As long as the primary power supply is turned on, whether it is no-load or loaded, the excitation circuit will always exist.

You should be talking about the excitation inrush current of the transformer:

The transformer excitation inrush current is: the transient current generated in the windings of a transformer when it is charged at full voltage. When the residual magnetic flux in the core before the transformer is put into operation and the magnetic flux generated by the working voltage when the transformer is put into operation, the total magnetic flux far exceeds the saturation magnetic flux of the core, so a large inrush current is generated, and the maximum peak can reach 6-8 times of the rated current of the transformer.

The excitation inrush current varies with the phase angle of the system voltage when the transformer is put into operation, the residual magnetic flux of the transformer core and the ground impedance of the power supply system, and the maximum inrush current occurs at the moment when the voltage passes through the zero point when the transformer is put into operation (the magnetic flux is the peak at that time). The transformer inrush current contains DC components and higher harmonic components, which decay with time, and its attenuation time depends on the loop resistance and reactance, generally about 5-10 seconds for large-capacity transformers and about seconds for small-capacity transformers.

When the transformer is in a state of power failure, the magnetic flux inside the transformer core is close to or equal to zero, when the transformer is charged, the alternating magnetic flux is generated in the iron core, and the alternating magnetic flux from zero to the maximum is called the core excitation, we call the current generated by this process called the transformer excitation inrush current, which is higher than the rated current of the transformer, from the mechanical force, electrodynamic force of the transformer to the protection setting to avoid the excitation inrush current setting.

The excitation inrush current (excitation current) of the transformer flows through only one side of the transformer. In steady-state operation, the excitation current of the transformer is not large, only 2-5% of the rated current. When the transformer is put in at no load and the voltage is restored after the external fault is removed, a large excitation current may occur, that is, the excitation inrush current.

The existence of this phenomenon is caused by the saturation of the transformer core and the presence of remanence, which is analyzed as follows

When the secondary side is open and the primary side is connected to the grid, the equation for the primary circuit is.

u1=umcos(wt+α)=i1r1+n1dφ/dt (1)

U1: primary voltage, U: peak value of primary voltage, initial phase angle of voltage at the moment of closing, R1: resistance of primary winding of transformer, N1: number of turns of primary winding of transformer, magnetic flux of primary side of transformer.

Since I1R1 is relatively small, it is negligible in the initial phase of the transient process so umcos(wt+)= n1d dt

dφ= ( um/ n1) cos(wt+α)dt

Points, get. =( um/ n1) sin(wt+α)c

m sin(wt+)c m is the main flux peak, and c is the integration constant.

Let the iron core have no remanence, when t=0, =0, so c=- msin

So the no-load closing flux is.

m sin(wt+ )msin can be obtained from the formula that the magnitude of the no-load closing flux is related to the initial phase angle of the voltage, and the most unfavorable case is considered.

When =90, the voltage crosses zero.

m sin(wt+900) -m=φmcoswt-φm

There are two components of magnetic flux, the periodic component mcoswt and the non-periodic component m, and the maximum value of the magnetic flux is twice that of the magnetic flux at steady state. If we also consider the effect of remanence, this value is even greater.

We know that transformers normally operate around the knee of the core magnetization curve, when the core is close to or slightly saturated. When the magnetic flux reaches more than 2 times m, the iron core is highly saturated, and the excitation current of the transformer increases significantly, up to 6 8 times of the rated current. The magnitude and decay time of the excitation inrush current are related to the applied voltage, the remanence size and direction of the core, the circuit impedance, the capacity of the transformer and the properties of the core.

The current can reach 6 8 times of the rated current, but the time process will not be too longSolution: Extend the transformer overcurrent protection action time (fixed time limit or reverse time limit) so that the transformer can not act when the overcurrent protection is airdropped.

It is the rated no-load current, the rated voltage is passed through once, the second open circuit, and the current value measured at one time.

The current used to establish magnetic flux.

The excitation current (excitingcurrent) is the current flowing through the rotor of the synchronous motor (with this current, the rotor is equivalent to an electromagnet, with n pole and S pole), and during normal operation, this current is generated by the DC voltage applied to the rotor externally.

This DC voltage is supplied by the DC motor, and most of it is supplied by the thyristor after rectification, and the thyristor rectifier system is usually called an excitation device.

Summary. Hello, it is a pleasure to serve you and give you the following answer: there is a close relationship between the main magnetic flux and the excitation current of the transformer, and the relationship between them can be expressed by the following formula:

Main Magnetic Flux = Excitation Current The permeability of the transformer If the main magnetic flux and excitation current of the transformer do not match, it may cause the transformer to fail. The methods and practical steps to solve this problem are as follows:1

First of all, check whether the permeability of the transformer is normal, if not, it should be replaced with a new permeability. 2.Check whether the excitation current of the transformer is normal, if not, it should be replaced with a new excitation current.

3.Check whether the main magnetic flux of the transformer is normal, if not, it should be replaced with a new main flux. 4.

Finally, check whether the magnetic circuit of the transformer is normal, if not, it should be replaced with a new one. Personal tip: When checking the main magnetic flux and excitation current of the transformer, the replacement parts should be determined according to the actual situation of the transformer to ensure the normal operation of the transformer.

The relationship between the main magnetic flux and the excitation current of the transformer.

Hello, it is a pleasure to serve you and give you the following answer: there is a close relationship between the main magnetic flux and the excitation current of the transformer, and the relationship between them can be expressed by the following formula: main magnetic flux = excitation current The permeability of the transformer If the main magnetic flux and excitation current of the transformer do not match, it may cause the transformer to fail.

The methods and practical steps to solve this problem are as follows:1First of all, check whether the permeability of the transformer is normal, if not, it should be replaced with a new permeability.

2.Check whether the excitation current of the transformer is normal, if not, it should be replaced with a new excitation current. 3.

Check whether the main magnetic flux of the transformer is normal, if not, it should be replaced with a new main flux. 4.Finally, check whether the magnetic circuit of the transformer is normal, if not, it should be replaced with a new one.

Personal tip: When checking the main magnetic flux and excitation current of the transformer, the replacement parts should be determined according to the actual situation of the transformer to ensure the normal operation of the transformer.

Can you add, I don't quite understand it.

Hello, it is a pleasure to serve you and give you the following answer: there is a close relationship between the main magnetic flux and the excitation current of the transformer, and the relationship between them can be expressed by the following formula: main magnetic flux = excitation current The permeability of the transformer If the main magnetic flux and excitation current of the transformer do not match, it may cause the transformer to fail.

The methods and practical steps to solve this problem are as follows:1First of all, check whether the permeability of the transformer is normal, if not, it should be replaced with a new permeability.

2.Check whether the excitation current of the transformer is normal, if not, it should be replaced with a new excitation current. 3.

Check whether the main magnetic flux of the transformer is normal, if not, it should be replaced with a new main flux. 4.Finally, check whether the magnetic circuit of the transformer is normal, if not, it should be replaced with a new one.

Personal tip: When checking the main magnetic flux and excitation current of the transformer, the replacement parts should be determined according to the actual situation of the transformer to ensure the normal operation of the transformer.

Summary. Hello dear, happy to answer your <>

The no-load current of the transformer is actually determined by the protection mechanism of the electrical equipment. When there is no external load between the two sides of the transformer (the high and low voltage side), the transformer current is small and almost negligible. This current is known as a no-load current.

Because the transformer is not loaded, the current is very small and is mainly used to magnetize the magnetic circuit inside the transformer, that is, the current of the core, which is also known as the excitation current. <>

The excitation current is necessary because it generates a magnetic field, which is a magnetic circuit that is used to change the voltage on the secondary side. The magnitude of the excitation current is determined by the characteristics of the transformer, and it is a very important parameter that affects the working efficiency, energy loss and temperature of the transformer.

Why can the no-load current of the transformer be called the excitation current?

Hello dear, happy to answer your <>

The no-load current of the transformer is actually determined by the protection mechanism of the electrical equipment. When there is no external load between the two sides of the transformer (the high and low voltage side), the transformer current is so small that it is almost negligible. This current is known as a no-load current.

Because the transformer is not loaded, the current is very small and is mainly used to magnetize the magnetic circuit inside the transformer, that is, the current of the core, which is also known as the excitation current. <>

The excitation current is necessary because it generates a magnetic field, which is a magnetic circuit that is used to change the voltage on the secondary side. The magnitude of the excitation current is determined by the characteristics of the transformer, and it is a very important parameter that affects the working efficiency, energy loss and temperature of the transformer.

Kiss, <>

Therefore, although no-load current and Laratsa magnetoelectric carry current are different concepts, their practical meaning is the same, both refer to the amount of current that passes through the transformer without any load.

The no-load current of the transformer is actually the current that the transformer flows through when the load is not connected. When the transformer is no-loaded, because there is no load current on the transformer winding, the magnetic flux generated by it can only be coupled into the core of the transformer through the magnetic circuit and air, so that the magnetic flux in the front core is constantly changing, and then the induced electromotive force is generated on the secondary side of the transformer. This process requires a certain Hukivolt current to maintain, which is the no-load current.

And this no-load current is also often referred to as the excitation current, because it is the current used to maintain the magnetic flux in the core, that is, it is the current used to "excite" the transformer. Therefore, excitation current and no-load current are actually the same concept, both refer to the current flowing through the transformer at no load.